Effect of FeVO₄ and Polyaniline Integration on the Electrochemical Performance of Supercapacitor Electrodes

In this study, iron vanadate (FeVO₄) nanostructures with varying Fe:V molar ratios (1:2, 1:3, 2:1, 3:1, and 1:1) were synthesized on nickel foam substrates using a hydrothermal method. To improve electrochemical performance, the optimal 1:1 Fe:V composition was further modified with polyaniline (PANI) via in situ oxidative polymerization. The morphology and structure of the prepared materials were examined using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and and Brunauer–Emmett–Teller (BET) surface area analysis confirming the successful formation of nanostructures and effective PANI incorporation. Electrochemical analyses including cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy demonstrated enhanced capacitance, energy density, and cycling performance due to the synergistic interaction between FeVO₄ and the conductive polymer. Among all compositions, the 1Fe:1 V/PANI electrode showed the highest specific capacitance (4.49 F/cm²) and longest discharge time (1706s), with 74.27% retention after 5000 cycles. The bare 1Fe:1 V electrode exhibited 64.11% stability and a specific capacitance of 2.80 F/cm². At low power densities (~ 1–2 mW/cm²), the composite electrode delivered an energy density of approximately 0.09 mWh/cm². These results indicate that composition optimization and conductive polymer integration are effective strategies to improve supercapacitor electrode performance.